The present invention relates to a magnetic material sputtering target, which contains boron (B) and is produced based on a powder sintering method; and particularly relates to a magnetic material target, in which the boron (B)-rich phase in the target is finely dispersed, and which reduces the generation of particles during sputtering, and is free from problems of mechanical properties such as cracks and useful for depositing films used in magnetic heads, magnetic resistance elements (MRAM) and the like, as well as to the production method thereof.
A tunnel magnetic resistance film having a high magnetoresistance effect is being used in magnetic heads and MRAMs, and magnetic substances including boron (B) are being used in the material that is used in the layer configuring these films. For example, known are compositions based on Co, Fe and boron such as Co—B, Fe—B, and Fe—Co—B, or compositions in which Al, Cu, Mn, Ni and the like are added thereto.
Generally speaking, when the composition of a B-containing magnetic substance of the tunnel magnetic resistance film is, for instance, Fe—Co—B, such film is produced by sputtering a Fe—Co—B sputtering target.
Since this kind of magnetic material sputtering target contains a large amount of B, in particular when the B composition ratio exceeds 10% and becomes high, an extremely brittle Fe boride phase of Fe2B or FeB, or a Co boride phase is formed. Consequently, with a sputtering target produced based on the melting method, the ingot would crack or become fractured, and it was difficult to obtain a sputtering target from such an ingot.
There is a method for producing a predetermined sputtering target by strictly managing the production process (refer to Patent Document 1), and this method yields a major advantage in that gas components such as oxygen can be reduced, but the difficulty of the production process cannot be denied.
Here, while there are various types of sputtering equipment, in the deposition of the foregoing magnetic substance film, a magnetron sputtering equipment comprising a DC power supply is widely used due to its high productivity. The sputtering method is a method in which a substrate as a positive electrode and a target as a negative electrode are placed opposite each other, and a high voltage is applied between the substrate and the target in an inert gas atmosphere to generate an electric field.
Hereat, the inert gas becomes ionized to form plasma made from electrons and positive ions. When the positive ions in the plasma collide with the surface of the target (negative electrode), the atoms configuring the target are ejected, and the ejected atoms become adhered onto the facing substrate surface to form a film. The sputtering method uses the principle that, through a sequence of these operations, the material configuring the target is deposited as a film on the substrate.
In light of the above, several prior patents have been proposed. For example, Patent Document 2 proposes: an Fe—Co—B-based alloy target material, wherein the diameter of the maximum inscribed circle that can be drawn in an area with no boride phase in a cross-sectional micro structure is 30 μm or less; and the said Fe—Co—B-based alloy target material, wherein the composition formula based on atomic ratio is (FeXCo100-X)100-YBY, 5≤X≤95, 5≤Y≤30.
The object of Patent Document 2 is to realize low magnetic permeability of the Fe—Co—B-based alloy target material for depositing a soft-magnetic film that is used in a perpendicular magnetic recording medium or a TMR element, and to provide an Fe—Co—B-based alloy target material that yields favorable sputtering characteristics. Nevertheless, in the foregoing case, there are drawbacks in that Patent Document 2 is inferior in terms of refinement and dispersibility of the boride phase, and characteristics as a sintered compact target are insufficient.
Moreover, Patent Document 3 discloses a soft-magnetic FeCo-based target material in which the atomic ratio of Fe:Co is 10:90 to 70:30 in the FeCo-based alloy. Patent Document 3 additionally discloses a soft-magnetic magnetic FeCo target material containing Al and/or Cr in an amount of 0.2 to 5.0 at %. Patent Document 3 further proposes an FeCo soft-magnetic target material additionally containing one or more types of B, Nb, Zr, Ta, Hf, Ti, and V in an amount of 30 at % or less.
Nevertheless, in the foregoing case, while Patent Document 3 describes that the sintering method or the casting method may be applied, Patent Document 3 makes no reference to the problem of the boride phase, and does not offer any solution to solve such problem.    [Patent Document 1] WO 2011/070860    [Patent Document 2] JP 2004-346423 A    [Patent Document 3] JP 2008-121071 A